Experimental Study of Parameters Influencing the Purity of Potassium Sulfate Fertilizer Produced from Jordanian Raw Materials

Home , Potassium sulfate

Mousa Gougazeh Natural Resources and Chemical Engineering Department, Faculty of Engineering Tafila Technical University, P.O. Box 179 Tafila 66110, Jordan

Abstract: The general objective of the present investigation was to make a contribution towards improving the purity of the produced potassium sulfate from (KCl, Arab Potash Company-Dead Sea) and (H2SO4, Jordanian Phosphate Company). The process parameters influencing the contamination of the poisoning chlorine within the product were experimentally investigated. The experiments were performed in a small-scale batch reactor equipped with a high temperature control system. The role of temperature was studied. Higher purity of potassium sulfate was achieved at higher temperatures. The effect of the quality of KCl used was investigated. It was found that implementing fine KCl as reagent is a dvantageous over standard KCl. A completely pure potassium sulfate fertilizer was produced after 110 minutes residence time in the case of using fine KCl.

Key words: K2SO4, purity, chlorine content, KCl reagent, particle size distribution

INTRODUCTION Dead Sea. In Jordan the produced potassium sulfate still does not meet the required agricultural The Dead Sea is the terminal lake of the Jordan specifications due to the existence of some harmful River System. Over the millennia, salts carried by the traces. This resulted from the low purity of KCl feed. river system - as well as discharges from many saline One of the major problems associated with the ground water sources - have accumulated in the lake, potassium sulfate production from Jordanian raw transforming it into one of the greatest mineral materials is its low purity, which resulted from the reservoirs on earth[1]. The Dead Sea measures 750 km2 inclusion of chlorine within the final solid product. This in area with an average of 370g of salt per kilogram of represents a challenge to meet the market water. It is the saltiest body of water on the planet. Its requirements[4-6]. surface is the lowest point on earth with a depth The main objective of the present study is to of 412 m. investigate the process parameters influencing the Extensive amounts of salt minerals are present in quality of potassium sulfate produced from Jordanian the Dead Sea, there are three major industrial minerals - potash and sulfuric acid and to evaluate its purity. The Carnallite (KCl.MgCl2. 6H2O), Sylvite (KCl) and parameters studied are particle size distribution and Langbeinite (K2SO4.2MgSO4). These economically temperature. valuable minerals have been extensively utilized for industrial applications, especially fertilizers. MATERIALS AND METHODS Over 43 billion tons of the salts are believed to be available in the Dead Sea, of which almost two billion The raw materials that implemented are potassium tons are potassium chloride. This makes it one of the chloride (fertilizer grade, 97% purity, average particle world's largest potash deposits. Arab Potash Company size of 100 µm) and sulfuric acid (93% purity) (APC) produces the Potash through evaporation from produced by wet process at Jordanian Phosphate ponds in Al-Safi, at the southern end of the Dead Sea. Company (JPC). The potassium chloride was crushed in The Dead Sea brine has a potash content of 1.2 %[2]. a jaw crusher, ground in a ball mill and sieved at 160 In Jordan about 90 % of the potassium chloride mesh (100 µm). In all experiments of the present study, (KCl) is produced as fertilizer grade of about 97 % standard and fine potassium chlorides (KCl) were used. purity, which also used as raw material for the production of potassium sulfate (K2SO4) fertilizer. The Experimental apparatus and procedures: The chemical grade or 99.9 % potassium chloride is the experimental apparatus consists of a small platinum basis for the manufacture of most potassium salts[3]. rounded batch reactor having a volume of 250 ml. The The present study of the potassium sulfate (K2SO4) reactor is covered with a led and equipped with a production was stimulated due to the presence of mechanical stirrer and thermocouple. It is placed in a appreciable and economical amounts of KCl in the muffle furnace with temperature control unit. Corresponding Author: Mousa Gougazeh, Natural Resources and Chemical Engineering Department, Faculty of Engineering, Tafila Technical University, P. O. Box 179 Tafila 66110, Jordan 139 Am. J. Environ. Sci., 1 (2):139-141, 2005

The experiments were conducted by introducing As presented in Fig. 1, at the initial stages of the the reagents to the reactor. The amounts added reaction after 60 min, the amount of chlorine content is according to the stoichiometry of the following very high due to the larger amounts of hydrochloric gas equation: absorbed by the liquid melt. The amount of chlorine then starts to decrease with time due to desorption of 2KCl + H2SO4 K2SO4 + 2HCl the generated hydrochloric gas from the melt. As depicted in Fig. 1, it was experimentally found that The reaction is performed at elevated temperature when the reaction proceeds at higher temperature, the where all reactants are present as a melt. The inclusion of chlorine within the melt (reaction mixture) temperature was controlled using the computerized is reduced remarkably. Higher temperatures can lead to program of the furnace in order to achieve the required decrease in the viscosity of the melt as well as an reaction temperature. Samples of the melt are increase of the kinetic energy of the produced gas. This withdrawn periodically, cooled and then analyzed to will contribute in facilitating the collapsing of the gas determine the chlorine content. bubbles and liberation (desorption) of the by-product hydrochloric acid gas from the liquid melt. The results RESULTS AND DISCUSSION obtained in Fig. 1 indicate that the fluid dynamics plays an important role on the rate of liberation of the gas An experimental study is conducted aiming to within the melt. The time elapsed to liberate the understand some parameters influencing the purity of produced gas can be reduced significantly by increasing potassium sulfate produced by reacting potassium the mixing intensity i.e. fluidity of the melt. An chloride with concentrated sulfuric acid. The most important parameter beside temperature and the fluid poisoning impurity, which affects the quality of dynamic is the pressure above the melt. Increasing the potassium sulfate and its availability as a fertilizer, is vacuum pressure accelerates the rate of desorption from the chlorine contents. The incorporated chlorine is the melt and higher purity can be achieved at lower resulted from the hydrochloric acid gas, which is temperatures. generated as a side product during the reaction. Controlling chlorine content can be achieved by a better Effect of the particle size distribution of the feed knowledge of the factors affecting the incorporation KCl: The influence of the particle size distribution of process of hydrochloric acid gas within the particles in the fed KCl on the purity of produced potassium sulfate the reaction mixture. was investigated by carrying out experiments with different size distribution qualities (standard and fine). The role of temperature: Temperature is the mostly The grain size analysis of both qualities is shown in important factor influencing the kinetics of the reaction Fig. 2. as well as the absorption/desorption rate of The amount of chlorine content in the melt during hydrochloric acid gas from the liquid melt or the the course of the reaction at a constant temperature of reaction medium. Figure 1 shows the influence of 500 ºC was analyzed in both cases where standard and temperature on the presence of chlorine during the fine KCl are fed as reactants. Th results are shown in course of the reaction between the sulfuric acid and Fig. 3. potassium chloride.

Fig.1: The measured chlorine content incorporated in Fig. 2: The particle size distribution of the the produced potassium sulfate during the course standard ad fine KCl used in the of reaction at different temperatures experiments

140 Am. J. Environ. Sci., 1 (2):139-141, 2005

Obviously, the amount of chlorine remaining in the CONCLUSION melt at the first stages (60-min) is much lower in the case of introducing fine crystals of KCl than the In the design of the operation of the batch standard KCl. Figure 3 shows that the total amount of reactor for the production of potassium sulfate fertilizer, chlorine can be completely separated after a relatively one of the mostly important parameters that must be considered is the temperature. The increase in the short time in the case of fine KCl. In the other hand, temperature can lead to more pure product due to the purification of the product cannot be achieved in the increase in the rate of desorption of HCl gas. The case of standard KCl. increase in fluidity by agitation and mixing can also reduce the chlorine contents. Also the size of the feed KCl is a parameter must be taken in account when considering the purity of the product. The introduction of finer KCl to the reactor results in the production of completely pure fertilizer.

REFERENCES

1. Bender, F., 1974. Geology of Jordan. Gebrueder

Borntraeer, Berlin, pp: 196. 2. Daniel, F., 1992. MDPA Ingenierie/Krebs, Battelle Europe and the Jordan Industrial Consortium Engineering Company. The Dead Sea Chemical Complex: Techno-Economic Study, Final Report. 3. Arthur, D., 1992. Further Evaluation of the Prospects for a Jordanian Potassium sulfate Plant, Fig. 3: The measured chlorine content at 500 ºC Final Report. in the reaction mixture when standard and 4. Tisdale, S.L., J.L. Havlin, J.D. Beaton and W.L. fine KCl are implemented as reactants Nelson, 1999. Soil Fertility and Fertilizers, An Introduction to Nutrient Management. 6th Ed. Prentice-Hall, Upper Saddle River, NJ. An important result can be extracted from Fig. 3 is 5. Ullmann, F., 2005. Ullmann's Encyclopediaof that the mean size of the feed KCl is an important Industrial Chemistry. John Wiley and Sons, Inc. parameter influencing the purity of the final product 6. Abu-Eishah, S.I., Bani-Kananeh, A.A., Allawazi, should be considered in the design and operation of the M.A., 2000. K2SO4 Production via the Double industrial reactor. This interpretation agrees with that Decomposition Reaction of KCl and discussed by Abu-Eishah et al.[6]. The more fine the Phosphogypsum, Chemical Engineering J., 76: feed crystals the easier and the faster the achievement 197-207. of pure potassium sulfate fertilizer.

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